Field of the Invention
This invention relates to flat panel display devices generally, and more particularly to processes for creating a template to align and adhere spacer structures which will provide support against the atmospheric pressure on a flat panel display without impairing the resolution of the image.
State of the Art
In flat panel displays of the field emission type, an evacuated cavity is maintained between the cathode electron-emitting surface and its corresponding anode display face. Spacer structures incorporated between the display face and the baseplate perform this function.
In order to be effective, spacer structures must possess certain characteristics. The spacer structures must be sufficiently non-conductive in order to prevent catastrophic electrical breakdown between the cathode array and the anode. In addition, they must exhibit sufficient mechanical strength to prevent the flat panel display from collapsing under atmospheric pressure. Furthermore, they must exhibit stability under electron bombardment, as electrons will be generated at each pixel location within the array. The spacer structures must be capable of withstanding xe2x80x9cbake-outxe2x80x9d temperatures of about 400xc2x0 C. that are likely to be used to create the vacuum between the screen and baseplate of the display. The spacers must also be sufficiently small in cross-sectional area, so as to be invisible during display operation.
It has been a challenge in the development of field emission displays (FED) to fabricate spacer structures because of the complex functional requirements they must possess.
Known methods using screen-printing, stencil printing, or glass balls do not provide a spacer having a sufficiently high aspect ratio. The spacers formed by these methods either cannot support the high voltages, or interfere with the display image. Other methods involving the etching of deposited materials suffer from slow throughput (i.e., time length of fabrication), slow etch rates, and etch mask degradation. The use of lithographically defined photoactive organic compounds results in the formation of spacers which are incompatible with the high vacuum conditions and elevated temperatures characteristic in the manufacture of field emission displays (FED).
Methods which employ the use of templates to align and attach the spacer structures to one of the electrode plates of the display have several drawbacks. The templates themselves are not refined enough to maintain the spacer in a sufficiently vertical position for attachment to the display electrode. Further, the prior art methods disclose the use of a sponge to apply an adhesive, such as glue, to the exposed ends of the spacers. The spacers are then mechanically aligned to an electrode plate to which they are attached. The glue emits a gas during subsequent processing, thereby contaminating the system.
Accordingly, there is a need for a high aspect ratio spacer structure for use in a FED, and an efficient method of manufacturing a FED with such a spacer.
One aspect of the present invention provides for a multi-layered template and includes the process for manufacturing such a template. The multi-layered process comprises anodically bonding at least one etch stop layer to at least one glass layer; patterning the layers; and then etching the layers to form an opening. This process can be repeated several times before disposing a spacer structure within the opening in the substrate.
Another aspect of the present invention comprises the process of using a multi-layered template having a spacer structure disposed therein to align the spacer structure to an electrode plate of a display device. The spacer can then be adhered to the baseplate or faceplate of the display through the use of an adhesive or, alternatively, by anodic bonding.
A further aspect of the present invention comprises the process of using a template having a spacer structure vertically disposed therein while anodically bonding the spacer structure to the faceplate or baseplate.